[yt-users] Angular momentum with a general axis

[Junhwan Choi (최준환)]

Hi yt users,

I wrote basic yt script to make Jz profile of my simulation as follow:
======
import matplotlib as matplotlib
matplotlib.use('Agg')
from yt.mods import *
import matplotlib.pyplot as plt

Nbin = 75
rmax = 1200 # in pc
index = 60

pf = load("../DD%04d/DD%04d" % (index,index))
rmin = [1e-4,2.0*pf.h.get_smallest_dx()*pf.units['pc']]
sphere = pf.h.sphere(center, (rmax, 'pc'))
bulk_velocity = sphere.quantities['BulkVelocity']()
sphere.set_field_parameter('bulk_velocity', bulk_velocity)

profile = BinnedProfile1D(sphere, Nbin, "Radiuspc", max(rmin), rmax,
log_space=True, lazy_reader=True, end_collect=False)
profile.add_fields('AngularMomentumZ',weight=None)
profile.add_fields('Radius',weight=None)

plt.loglog(profile['Radiuspc'],
profile['AngularMomentumZ'],label='t=%4.2fMyr' %
(pf.current_time*7.26), linestyle="-",color='b')
plt.xlabel('r [pc]')
plt.ylabel(r'j ($\rm{cm}^2/\rm{s}$)',fontsize=17)
plt.xlim(1e-4,1000)
plt.legend(loc=4, prop={'size':10})
plt.savefig('jprof2K_%04d' % index)
=========

Now I would like to compute the AngularMomentum not according to x,
y,and z but according to a general axis (i.e. angular momentum axis).
Is there any simple way in yt to compute the AngularMomentum according
to the general axis?

Thank you in advance,
Junhwan